OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..1000
EXAMPLE
1531 gives primes 53, 131 and 151 after dropping digits 1, 5 and 3.
A larger example 1210778071 gives primes 12177871, 2077807, 110778071, 1210801 and 121077071 after dropping digits 0, 1, 2, 7 and 8.
MAPLE
filter:= proc(n) local L, d, Lp;
if not isprime(n) then return false fi;
L:= convert(n, base, 10);
for d in convert(L, set) do
Lp:= subs(d=NULL, L);
if Lp=[] or Lp[-1] = 0 then return false fi;
if not isprime(add(Lp[i]*10^(i-1), i=1..nops(Lp))) then return false fi;
od;
true
end proc:
select(filter, [seq(i, i=13..20000, 2)]); # Robert Israel, Jul 13 2018
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Oct 15 2000
EXTENSIONS
Name edited by Robert Israel, Jul 13 2018
STATUS
approved